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  • 251.
    Ganjei, Zeinab
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Rezine, Ahmed
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Eles, Petru Ion
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Safety Verification of Phaser Programs2017In: PROCEEDINGS OF THE 17TH CONFERENCE ON FORMAL METHODS IN COMPUTER AIDED DESIGN (FMCAD 2017), IEEE , 2017, p. 68-75Conference paper (Refereed)
    Abstract [en]

    We address the problem of statically checking control state reachability (as in possibility of assertion violations, race conditions or runtime errors) and plain reachability (as in deadlock-freedom) of phaser programs. Phasers are a modern non-trivial synchronization construct that supports dynamic parallelism with runtime registration and deregistration of spawned tasks. They allow for collective and point-to-point synchronizations. For instance, phasers can enforce barriers or producer-consumer synchronization schemes among all or subsets of the running tasks. Implementations are found in modern languages such as Habanero Java. Phasers essentially associate phases to individual tasks and use their runtime values to restrict possible concurrent executions. Unbounded phases may result in infinite transition systems even in the case of programs only creating finite numbers of tasks and phasers. We introduce an exact gap-order based procedure that always terminates when checking control reachability for programs generating bounded numbers of coexisting tasks and phasers. We also show verifying plain reachability is undecidable even for programs generating few tasks and phasers. We then explain how to turn our procedure into a sound analysis for checking plain reachability (including deadlock freedom). We report on preliminary experiments with our open source tool.

  • 252.
    Ganjei, Zeinab
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Rezine, Ahmed
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Abstracting and Counting Synchronizing Processes2014Report (Other academic)
    Abstract [en]

    We address the problem of automatically establishing synchronization dependent correctness (e.g. due to using barriers or ensuring absence of deadlocks) of programs generating an arbitrary number of concurrent processes and manipulating variables ranging over an infinite domain. Automatically checking such properties for these programs is beyond the capabilities of current verification techniques. For this purpose, we describe an original logic that mixes two sorts of variables: those shared and manipulated by the concurrent processes, and ghost variables refering to the number of processes satisfying predicates on shared and local program variables. We then combine existing works on counter, predicate, and constrained monotonic abstraction and nest two cooperating counter example based refinement loops for establishing correctness (safety expressed as non reachability of configurations satisfying formulas in our logic). We have implemented a tool (Pacman, for predicated constrained monotonic abstraction) and used it to perform parameterized verification for several programs whose correctness crucially depends on precisely capturing the number of synchronizing processes. 

  • 253.
    Ganjei, Zeinab
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Rezine, Ahmed
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Counting dynamically synchronizing processes2016In: International Journal on Software Tools for Technology Transfer (STTT), ISSN 1433-2779, E-ISSN 1433-2787, Vol. 18, no 5, p. 517-534Article in journal (Refereed)
    Abstract [en]

    We address the problem of automatically establishing correctness for programs generating an arbitrary number of concurrent processes and manipulating variables ranging over an infinite domain. The programs we consider can make use of the shared variables to count and synchronize the spawned processes. This allows them to implement intricate synchronization mechanisms, such as barriers. Automatically verifying correctness, and deadlock freedom, of such programs is beyond the capabilities of current techniques. For this purpose, we make use of counting predicates that mix counters referring to the number of processes satisfying certain properties and variables directly manipulated by the concurrent processes. We then combine existing works on counter, predicate, and constrained monotonic abstraction and build a nested counter example based refinement scheme for establishing correctness (expressed as non-reachability of configurations satisfying counting predicates formulas). We have implemented a tool (Pacman, for predicated constrained monotonic abstraction) and used it to perform parameterized verification on several programs whose correctness crucially depends on precisely capturing the number of processes synchronizing using shared variables.

  • 254.
    Ganjei, Zeinab
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Rezine, Ahmed
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Lazy Constrained Monotonic Abstraction2016In: Verification, Model Checking, and Abstract Interpretation: 17th International Conference, VMCAI 2016, St. Petersburg, FL, USA, January 17-19, 2016. Proceedings / [ed] Barbara Jobstmann; K. Rustan M. Leino, Springer Berlin/Heidelberg, 2016, Vol. 9583, p. 147-165Conference paper (Refereed)
    Abstract [en]

    We introduce Lazy Constrained Monotonic Abstraction (lazy CMA for short) for lazily and soundly exploring well structured abstractions of infinite state non-monotonic systems. CMA makes use of infinite state and well structured abstractions by forcing monotonicity wrt. refinable orderings. The new orderings can be refined based on obtained false positives in a CEGAR like fashion. This allows for the verification of systems that are not monotonic and are hence inherently beyond the reach of classical analysis based on the theory of well structured systems. In this paper, we consistently improve on the existing approach by localizing refinements and by avoiding to trash the explored state space each time a refinement step is required for the ordering. To this end, we adapt ideas from classical lazy predicate abstraction and explain how we address the fact that the number of control points (i.e., minimal elements to be visited) is a priori unbounded. This is unlike the case of plain lazy abstraction which relies on the fact that the number of control locations is finite. We propose several heuristics and report on our experiments using our open source prototype. We consider both backward and forward explorations on non-monotonic systems automatically derived from concurrent programs. Intuitively, the approach could be regarded as using refinable upward closure operators as localized widening operators for an a priori arbitrary number of control points.

  • 255.
    Ganjei, Zeinab
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Rezine, Ahmed
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Ion Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Abstracting and Counting Synchronizing Processes2015In: Verification, Model Checking, and Abstract Interpretation: 16th International Conference on Verification, Model Checking, and Abstract Interpretation (VMCAI 2015), Mumbai, India, Jan. 12-14, 2015., Springer, 2015, p. 227-244Conference paper (Refereed)
    Abstract [en]

    We address the problem of automatically establishing synchronization dependent correctness (e.g. due to using barriers or ensuring absence of deadlocks) of programs generating an arbitrary number of concurrent processes and manipulating variables ranging over an infinite domain. Automatically checking such properties for these programs is beyond the capabilities of current verification techniques. For this purpose, we describe an original logic that mixes two sorts of variables: those shared and manipulated by the concurrent processes, and ghost variables referring to the number of processes satisfying predicates on shared and local program variables. We then combine existing works on counter, predicate, and constrained monotonic abstraction and nest two cooperating counter example based refinement loops for establishing correctness (safety expressed as non reachability of configurations satisfying formulas in our logic). We have implemented a tool (Pacman, for predicated constrained monotonic abstraction) and used it to perform parameterized verification for several programs whose correctness crucially depends on precisely capturing the number of synchronizing processes.

  • 256.
    Ganty, Pierre
    et al.
    IMDEA Software Institute, Spain.
    Rezine, Ahmed
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Ordered Counter-Abstraction Refinable Subword Relations for Parameterized Verification2014In: LANGUAGE AND AUTOMATA THEORY AND APPLICATIONS (LATA 2014), Springer Berlin/Heidelberg, 2014, Vol. 8370, p. 396-408Conference paper (Refereed)
    Abstract [en]

    We present an original refinable subword based symbolic representation for the verification of linearly ordered parameterized systems. Such a system consists of arbitrary many finite processes placed in an array. Processes communicate using global transitions constrained by their relative positions (i.e., priorities). The model can include binary communication, broadcast, shared variables or dynamic creation and deletion of processes. Configurations are finite words of arbitrary lengths. The successful monotonic abstraction approach uses the subword relation to define upward closed sets as symbolic representations for such systems. Natural and automatic refinements remained missing for such symbolic representations. For instance, subword based relations are simply too coarse for automatic forward verification of systems involving priorities. We remedy to this situation and introduce a symbolic representation based on an original combination of counter abstraction with subword based relations. This allows us to define an infinite family of relaxation operators that guarantee termination by a new well quasi ordering argument. The proposed automatic analysis is at least as precise and efficient as monotonic abstraction when performed backwards. It can also be successfully used in forward, something monotonic abstraction is incapable of. We implemented a prototype to illustrate the approach.

  • 257.
    Garro, Alfredo
    et al.
    Department of Informatics, Modeling, Electronics and Systems Engineering (DIMES), University of Calabria, Italy.
    Tundis, Andrea
    Department of Informatics, Modeling, Electronics and Systems Engineering (DIMES), University of Calabria, Italy.
    Bouskela, Daniel
    R&D Division, Electricité de France (EDF), France.
    Jardin, Audrey
    R&D Division, Electricité de France (EDF), France.
    Nguyen, Thuy
    R&D Division, Electricité de France (EDF), France.
    Otter, Martin
    Institute of System Dynamics and Control, DLR German Aerospace Center, Germany.
    Buffoni, Lena
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Fritzson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Sjölund, Martin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Schamai, Wladimir
    Airbus Group Innovations, Hamburg, Germany.
    Olsson, Hans
    Dassault Systèmes AB, Sweden.
    On formal cyber physical system properties modeling: a new temporal logic language and a Modelica-based solution2016In: 2016 IEEE International Symposium on Systems Engineering (ISSE), IEEE , 2016, p. 112-119Conference paper (Refereed)
    Abstract [en]

    Modeling and Simulation methods, tools and techniques aim at supporting the different phases of the lifecycle of modern systems, going from requirements analysis to system design and operation. However, their effective application requires investigating several aspects such as the formal modeling of system requirements and the binding and automated composition between heterogeneous models (e.g. requirements models, architectural models, behavioral models). In this context, the paper presents a new formal requirement modeling language based on temporal logic, called FORM-L, and a software library, based on the Modelica language, that implements the constructs provided by FORM-L so as to enable the visual modeling of system properties as well as their verification through simulation. The effectiveness of the proposal is shown on a real case study concerning an Intermediate Cooling System.

  • 258.
    Gatla, Goutham
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Validation of ModelicaML models2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the world of modeling, Model Validation plays a crucial role. A model editor is not said to becomplete without Validation. ModelicaML is a Modeling Language extended from a subset of UMLand SysML, developed under OpenModelica Project. It is defined to provide time-discrete andtime-continuous models. Papyrus Model Editor is extended to support for ModelicaML usingModelicaML Eclipse plug-in. This plug-in comes with Modelica Code Generator.Previously, ModelicaML plug-in had a prototype of validation which provided only Batch-modevalidation. The validation is used to be done by the Modelica compiler after the code generation phase.Each time the user tried to validate the model; first Modelica code is generated and then validated. Thistype of validation misses certain validation rules to validate due to the conversion from theModelicaML model to Modelica code.The goal of this thesis is to implement Model Validation done at model editor level with both Batch andLive mode validation. This can be done by developing an Eclipse plug-in which does the ModelValidation. This plug-in uses the EMF Validation framework for implementing the constraints andvalidation on ModelicaML models.

  • 259.
    Gavrilut, Voica
    et al.
    Tech Univ Denmark, Denmark.
    Zarrin, Bahram
    Tech Univ Denmark, Denmark.
    Pop, Paul
    Tech Univ Denmark, Denmark.
    Samii, Soheil
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. Gen Motors RandD, MI USA.
    Fault-Tolerant Topology and Routing Synthesis for IEEE Time-Sensitive Networking2017In: PROCEEDINGS OF THE 25TH INTERNATIONAL CONFERENCE ON REAL-TIME NETWORKS AND SYSTEMS (RTNS 2017), ASSOC COMPUTING MACHINERY , 2017, p. 267-276Conference paper (Refereed)
    Abstract [en]

    Time-Sensitive Networking (TSN) is a set of IEEE standards that extend Ethernet for safety-critical and real-time applications. TSN is envisioned to be widely used in several applications areas, from industrial automation to in-vehicle networking. A TSN network is composed of end systems interconnected by physical links and bridges (switches). The data in TSN is exchanged via streams. We address safety-critical real-time systems, and we consider that the streams use the Urgency-Based Scheduler (UBS) traffic-type, suitable for hard real-time traffic. We are interested in determining a fault-tolerant network topology, consisting of redundant physical links and bridges, the routing of each stream in the applications, such that the architecture cost is minimized, the applications are fault-tolerant (i.e., the critical streams have redundant disjoint routes), and the timing constraints of the applications are satisfied. We propose three approaches to solve this optimization problem: (1) a heuristic solution, (2) a Greedy Randomized Adaptive Search Procedure (GRASP) metaheuristic, and (3) a Constraint Programming based model. The approaches are evaluated on several test cases, including a test case from General Motors Company.

  • 260.
    Gebremedhin, Mahder
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Automatic and Explicit Parallelization Approaches for Equation Based Mathematical Modeling and Simulation2018Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The move from single-core processor systems to multi-core and manyprocessor systems comes with the requirement of implementing computations in a way that can utilize these multiple computational units efficiently. This task of writing efficient parallel algorithms will not be possible without improving programming languages and compilers to provide the supporting mechanisms. Computer aided mathematical modelling and simulation is one of the most computationally intensive areas of computer science. Even simplified models of physical systems can impose a considerable computational load on the processors at hand. Being able to take advantage of the potential computational power provided by multi-core systems is vital in this area of application. This thesis tries to address how to take advantage of the potential computational power provided by these modern processors in order to improve the performance of simulations, especially for models in the Modelica modelling language compiled and simulated using the OpenModelica compiler and run-time environment.

    Two approaches of utilizing the computational power provided by modern multi-core architectures for simulation of Mathematical models are presented in this thesis: Automatic and Explicit parallelization respectively. The Automatic approach presents the process of extracting and utilizing potential parallelism from equation systems in an automatic way without any need for extra effort from the modellers/programmers. This thesis explains new and improved methods together with improvements made to the OpenModelica compiler and a new accompanying task systems library for efficient representation, clustering, scheduling, profiling, and executing complex equation/ task systems with heavy dependencies. The Explicit parallelization approach allows utilizing parallelism with the help of the modeller or programmer. New programming constructs have been introduced to the Modelica language in order to enable modellers to express parallelized algorithms to take advantage of the computational capabilities provided by modern multicore CPUs and GPUs. The OpenModelica compiler has been improved accordingly to recognize and utilize the information from these new algorithmic constructs and to generate parallel code for enhanced computational performance, portable to a range of parallel architectures through the OpenCL standard.

  • 261.
    Gebremedhin, Mahder
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Automatic and Explicit Parallelization Approaches for Mathematical Simulation Models2015Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The move from single core and processor systems to multi-core and many-processors systemscomes with the requirement of implementing computations in a way that can utilizethese multiple units eciently. This task of writing ecient multi-threaded algorithmswill not be possible with out improving programming languages and compilers to providethe mechanisms to do so. Computer aided mathematical modeling and simulationis one of the most computationally intensive areas of computer science. Even simpli-ed models of physical systems can impose a considerable amount of computational loadon the processors at hand. Being able to take advantage of the potential computationpower provided by multi-core systems is vital in this area of application. This thesis triesto address how we can take advantage of the potential computation power provided bythese modern processors to improve the performance of simulations. The work presentsimprovements for the Modelica modeling language and the OpenModelica compiler.

    Two approaches of utilizing the computational power provided by modern multi-corearchitectures are presented in this thesis: Automatic and Explicit parallelization. Therst approach presents the process of extracting and utilizing potential parallelism fromequation systems in an automatic way with out any need for extra eort from the modelers/programmers side. The thesis explains improvements made to the OpenModelicacompiler and presents the accompanying task systems library for ecient representation,clustering, scheduling proling and executing complex equation/task systems with heavydependencies. The Explicit parallelization approach explains the process of utilizing parallelismwith the help of the modeler or programmer. New programming constructs havebeen introduced to the Modelica language in order to enable modelers write parallelizedcode. the OpenModelica compiler has been improved accordingly to recognize and utilizethe information from this new algorithmic constructs and generate parallel code toimprove the performance of computations.

  • 262.
    Gebremedhin, Mahder
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Fritzson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Automatic Task Based Analysis and Parallelization in the Context of Equation Based Languages2014In: EOOLT '14 Proceedings of the 6th International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools, New York: ACM , 2014, p. 49-52Conference paper (Refereed)
    Abstract [en]

    This paper presents an automatic parallelization approach for handling complex task systems with heavy dependencies, including methods of analyzing dependencies, representing them in a convenient way, and processing the resulting task graph representation. We present a library-based task system representation, clustering, profiling, and scheduling approach to simplify the otherwise tedious process of parallelizing complex task systems. We have implemented a flexible and robust task system handling library to manipulate and parallelize these complex task systems on shared memory multi-core and multi-processor systems. The implementation has been developed as part of the OpenModelica simulation environment. We demonstrate methods of extracting and utilizing parallelism in the context of mathematical modeling languages.

  • 263.
    Gerling, Jonas
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Implementing Object and Feature Detection Without Compromising the Performance2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis will cover how some computationally heavy algorithms used in digital image processing and computer vision are implemented with WebGL and computed on the graphics processing unit by utilizing GLSL-shaders. This thesis is based on an already implemented motion detection plug-in used in web based games. This plug-in is enhanced with new features and some already implemented algorithms are improved. The motion detection is based on image subtraction and uses the delta image from previous frames to determine motion.

    The plug-in is used in web based games so the performance is of utmost importance since bad performance leads to frustration and less immersion for the players

    Techniques brought up are edge detection, Gaussian filter, features from accelerated segment test(FAST) and Harris corner detection. These techniques will be implemented by utilizing the parallel structure of the GPU. Both Harris corner detection and features from accelerated segment test can be run in real time but the result of the Harris corner detection is the better of the two. The thesis will also cover different color spaces, how they are implemented and why they were implemented

  • 264.
    Ghani Zadegan, Farrokh
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Ingelsson, Urban
    Semcon AB.
    Carlsson, Gunnar
    Ericsson AB.
    Larsson, Erik
    Lund University, Sweden .
    Access Time Analysis for IEEE P16872012In: I.E.E.E. transactions on computers (Print), ISSN 0018-9340, E-ISSN 1557-9956, Vol. 61, no 10, p. 1459-1472Article in journal (Refereed)
    Abstract [en]

    The IEEE P1687 (IJTAG) standard proposal aims at providing a standardized interface between the IEEE Standard 1149.1 test access port (TAP) and on-chip embedded test, debug and monitoring logic (instruments), such as scan chains and temperature sensors. A key feature in P1687 is to include Segment Insertion Bits (SIBs) in the scan path to allow flexibility both in designing the instrument access network and in scheduling the access to instruments. This paper presents algorithms to compute the overall access time (OAT) for a given P1687 network. The algorithms are based on analysis for flat and hierarchical network architectures, considering two access schedules, i.e., concurrent schedule and sequential schedule. In the analysis, two types of overhead are identified, i.e., network configuration data overhead and JTAG protocol overhead. The algorithms are implemented and employed in a parametric analysis and in experiments on realistic industrial designs.

  • 265.
    Gillsjö, Lukas
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Using OpenCL to Implement Median Filtering and RSA Algorithms: Two GPGPU Application Case Studies2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Graphics Processing Units (GPU) and their development tools have advanced recently, and industry has become more interested in using them. Among several development frameworks for GPU(s), OpenCL provides a programming environment to write portable code that can run in parallel. This report describes two case studies of algorithm implementations in OpenCL. The first algorithm is Median Filtering which is a widely used image processing algorithm. The other algorithm is RSA which is a popular algorithm used in encryption. The CPU and GPU implementations of these algorithms are compared in method and speed. The GPU implementations are also evaluated by efficiency, stability, scalability and portability. We find that the GPU implementations perform better overall with some exceptions. We see that a pure GPU solution is not always the best and that a hybrid solution with both CPU and GPU may be to prefer in some cases.

  • 266.
    Girma, Robi
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Evaluation of container virtualization systems supporting Open Container Initiative images2018Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Abstract

    In the Virtualization industry, container virtualization has increased in popularity with the emergence of container engines in 2013. Container engines create, remove and manage containers. They do so by utilizing container images from which containers are created. Images work as templates, are reusable and can be uploaded for others to download. Big contributors in the field of container virtualization grouped up and founded the Open Container Initiative. The project established an industry standard for the architecture of container images and how they should be run.

     

    The IT consultant company Zenon has requested a thesis to be done in the field of container virtualization as they are thinking of starting to work with one but want to learn more about modern solutions. Due to the lack of back-to-back comparisons of modern solutions supporting the standard set by the Open Container Initiative, this thesis makes an evaluation of available systems in industry standard terms of performance. The company is also interested in fields; isolation, image management and time to build an image of a Zenon application and deploy a container from it.

     

    The evaluation in this thesis was made on container engines Docker and rkt. Results showed that Docker performed better in all benchmarks. Rkt starts a container in less time than Docker but takes longer to build the specified image. Docker has much more capabilities in terms of image management with the ability to create images from scratch and to run on multiple operating systems, while rkt has limited ability for creating images, requires more configurations and is exclusive available for Linux. Both container engines offer varied isolation, where Docker has 2 security profiles and rkt lets the user implement custom isolation profiles with several provided options available.

  • 267.
    Glasser, Christian
    et al.
    University of Wurzburg, Germany.
    Jonsson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Martin, Barnaby
    Middlesex University, England.
    Circuit Satisfiability and Constraint Satisfaction Around Skolem Arithmetic2016In: Pursuit of the Universal, SPRINGER INT PUBLISHING AG , 2016, Vol. 9709, p. 323-332Conference paper (Refereed)
    Abstract [en]

    We study interactions between Skolem Arithmetic and certain classes of Circuit Satisfiability and Constraint Satisfaction Problems (CSPs). We revisit results of Gla beta er et al. [16] in the context of CSPs and settle the major open question from that paper, finding a certain satisfiability problem on circuits-involving complement, intersection, union and multiplication-to be decidable. This we prove using the decidability of Skolem Arithmetic. Then we solve a second question left open in [16] by proving a tight upper bound for the similar circuit satisfiability problem involving just intersection, union and multiplication. We continue by studying first-order expansions of Skolem Arithmetic without constants, (N; x), as CSPs. We find already here a rich landscape of problems with non-trivial instances that are in P as well as those that are NP-complete.

  • 268.
    Glasser, Christian
    et al.
    Julius Maximilian University, Germany.
    Jonsson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Martin, Barnaby
    University of Durham, England.
    Circuit satisfiability and constraint satisfaction around Skolem Arithmetic2017In: Theoretical Computer Science, ISSN 0304-3975, E-ISSN 1879-2294, Vol. 703, p. 18-36Article in journal (Refereed)
    Abstract [en]

    We study interactions between Skolem Arithmetic and certain classes of Circuit Satisfiability and Constraint Satisfaction Problems (CSPs). We revisit results of Glasser et al. [1] in the context of CSPs and settle the major open question from that paper, finding a certain satisfiability problem on circuits-involving complement, intersection, union and multiplication-to be decidable. This we prove using the decidability of Skolem Arithmetic. Then we solve a second question left open in [1] by proving a tight upper bound for the similar circuit satisfiability problem involving just intersection, union and multiplication. We continue by studying first-order expansions of Skolem Arithmetic without constants, (N; x), as CSPs. We find already here a rich landscape of problems with non-trivial instances that are in P as well as those that are NP-complete. (C) 2017 Elsevier B.V. All rights reserved.

  • 269.
    Gomes de Oliveira Neto, Francisco
    et al.
    Chalmers/University of Gothenburg, Sweden.
    Ahmad, Azeem
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Leifler, Ola
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Sandahl, Kristian
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Enoiu, Eduard
    Mälardalen University, Sweden.
    Improving continuous integration with similarity-based test case selection2018In: Proceedings of the 13th International Workshop on Automation of Software Test, New York: ACM Digital Library, 2018, p. 39-45Conference paper (Refereed)
    Abstract [en]

    Automated testing is an essential component of Continuous Integration (CI) and Delivery (CD), such as scheduling automated test sessions on overnight builds. That allows stakeholders to execute entire test suites and achieve exhaustive test coverage, since running all tests is often infeasible during work hours, i.e., in parallel to development activities. On the other hand, developers also need test feedback from CI servers when pushing changes, even if not all test cases are executed. In this paper we evaluate similarity-based test case selection (SBTCS) on integration-level tests executed on continuous integration pipelines of two companies. We select test cases that maximise diversity of test coverage and reduce feedback time to developers. Our results confirm existing evidence that SBTCS is a strong candidate for test optimisation, by reducing feedback time (up to 92% faster in our case studies) while achieving full test coverage using only information from test artefacts themselves.

  • 270.
    Gorm Larsen, Peter
    et al.
    Aarhus University, Denmark.
    Fitzgerald, John
    Newcastle University, England.
    Woodcock, Jim
    University of York, England.
    Fritzson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Brauer, Joerg
    Verified Syst Int, Germany.
    Kleijn, Christian
    Controllab Prod, Netherlands.
    Lecomte, Thierry
    Clearsy SAS, France.
    Pfeil, Markus
    TWT Science and Innovat, Germany.
    Green, Ole
    Agro Intelligence, Denmark.
    Basagiannis, Stylianos
    United Technology Research Centre, Ireland.
    Sadovykh, Andrey
    Softeam, France.
    Integrated Tool Chain for Model-based Design of Cyber-Physical Systems: The INTO-CPS Project2016In: 2016 2ND INTERNATIONAL WORKSHOP ON MODELLING, ANALYSIS, AND CONTROL OF COMPLEX CPS (CPS DATA), IEEE , 2016Conference paper (Refereed)
    Abstract [en]

    We describe INTO-CPS, a project that aims to realise the goal of integrated tool chains for the collaborative and multidisciplinary engineering of dependable Cyber-Physical Systems (CPSs). Challenges facing model-based CPS engineering are described, focussing on the semantic diversity of models, management of the large space of models and artefacts produced in CPS engineering, and the need to evaluate effectiveness in industrial settings. We outline the approach taken to each of these issues, particularly on the use of semantically integrated multi-models, links to architectural modelling, code generation and testing, and evaluation via industry-led studies. We describe progress on the development of a prototype tool chain from baseline tools, and discuss ongoing challenges and open research questions in this area.

  • 271.
    Grahn, Ivar
    Linköping University, Department of Computer and Information Science, Software and Systems.
    The Vuforia SDK and Unity3D Game Engine: Evaluating Performance on Android Devices2017Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    This paper evaluates major features of PTC’s augmented reality SDK Vuforia, available for Android, iOS and the Unity3D game engine. The performance of these features are evaluated in terms of frame rate and power consumption and the testing prototypes are developed using Unity3D. Augmented reality is a rapidly growing medium and the Vuforia SDK is very popular with over 325 000 registered developers and thousands of published applications. Despite being used to such extents, there are surprisingly few works evaluating different aspects of its performance. This paper provides an introduction to augmented reality and describes the technology used by the Vuforia SDK to deliver said features. This paper shows that Vuforia is capable of maintaining sufficient performance with interactive frame rates over 20 Hz in most cases. The power consumption of these features reduces the battery lifetime to acceptable levels, suitable for hand-held devices. In some cases, however, the performance in terms of frame rate reaches levels lower than recommended. These cases should be considered by developers looking to use Vuforia.

  • 272.
    Grape, Victor
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Comparing Costs of Browser Automation Test Tools with Manual Testing2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Testing is a necessary component of software development, but it is also an expensive one, especially if performed manually. One way to mitigate the cost of testing is to implement test automation, where the test cases are run automatically. For any organisation looking to implement test automation, the most interesting cost is time. Automation takes time to implement and one of the most obvious benefits of automation is that the automated test execution time is lower than that of manual execution. This thesis contains a literature study covering testing methodology, especially in regards to the domain of web application testing. The literature covered also included three economic models that may be used to calculate the costs of automation compared to manual testing. The models can be used to calculate the time it would take, or the number of necessary executions, for the total cost of test automation to be lower than of that of manual testing. The thesis is based on a case study of test automation for the StoredSafe platform, a web application. Three sets of test automation frameworks were used to implement three different test suits and the test implementation times were collected. The data collected were then used to calculate the time it would take, using the three economic models, for the cost of automated test cases to become equal to that of with manual testing. The data showed that the estimated time to reach breakeven for the three frameworks varied between 2½ and at worst 10 years, with an average of 3½ years. The models and data presented in this thesis may be used in order to estimate the cost of test automation in comparison to manual testing over longer periods of time, but care must be taken in order to ensure that the data used is correct in regards to one’s own organisation or else the estimate may be faulty.

  • 273.
    Green Olander, Jens
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Optimizing Communication Energy Efficiency for a Multimedia Application2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Mobile devices have evolved rapidly in recent years and increased usage and performance are pushing contemporary battery technology to its limits. The constrained battery resources mean that the importance of energy-efficient application design is growing and in this regard wireless network accesses are a major contributor to a mobile device's overall energy consumption. Additionally, the energy consumption characteristics of modern cellular technologies make small volumes of poorly scheduled traffic account for a substantial share of a device's total energy consumption. However, quantifying the communication energy footprint is cumbersome, making it difficult for developers to profile applications from an energy consumption perspective and optimize traffic patterns.

    This thesis examines the traffic patterns of the Android client of the popular multimedia streaming service Spotify with the intention to reduce its energy footprint, in terms of 3G energy consumption. The application's automated test environment is extended to capture network traffic, which is used to estimate energy consumption. Automated system tests are designed and executed on a physical Android device connected to a 3G network, shedding light on the traffic patterns of different application features.

    All traffic between the Spotify client application and the backend servers is encrypted. To extract information about the traffic, the application code is instrumented to output supplementary information to the Android system log. The system log is then used as a source of information to attribute data traffic to different application modules and specific lines of code.

    Two simple traffic shaping techniques, traffic aggregation and piggybacking, are implemented in the application to provide more energy-efficient traffic patterns. As a result, 3G energy consumption during normal music playback is reduced by 22-54%, and a more contrived scenario achieves a 60% reduction. The reductions are attained by rescheduling a small class of messages, most notably data tracking application usage. These messages were found to account for a small fraction of total traffic volume, but a large portion of the application's overall 3G energy consumption.

  • 274.
    Grundström, Niklas
    Linköping University, Department of Computer and Information Science, Software and Systems.
    A Security Analysis of a Credit Card Payment System for Bitcoin Transactions2018Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Cryptocurrencies has become a very hot topic recently, with Bitcoin being the most

    popular. The increase in interest has led to an incentive to create payment systems for the

    currency that makes it easier to use for day-to-day shopping. A lot of companies are inves-

    tigating possible solutions for credit cards that are used for cryptocurrencies. This thesis

    aims to present and perform a security analysis on an already created concept of a credit

    card payment system for Bitcoin. The security analysis is done in a systematical approach

    where the modules were analyzed with predetermined restrictions and assumptions. The

    restricitons and assumptions are then removed one-by-one to find potential threats in the

    system. The outcome of the analysis is then evaluated in an attempt to find possible im-

    plementation methods that would mitigate or prevent the discovered threats. The possible

    implementations are also evaluated in terms of how they would affect the system.

  • 275.
    Gustafsson, Anders
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Use of head mounted virtual reality displays in flight training simulation2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this thesis was to evaluate currently commercially available head mounted virtual reality displays for potential use in pilot training simulators. For this purpose acommercial simulator was modified to display the virtual environment in an Oculus RiftDK2 headset. A typical monitor based setup was used to provide a set of hardware requirements which the VR implementation had to meet or exceed to be considered potentially usable for pilot training simulators. User tests were then performed with a group of users representative of those normally using pilot training simulators, including both pilots and engineers working with simulator development. The main focus of the user tests was to evaluate some potential weaknesses found in the technical comparison (such as when a measured parameter was close to the lower limit defined by the monitor based setup) and to make a measurement of the usability of the VR implementation. The results from the technical comparison showed that the technical requirements were met and in most cases also exceeded. There were however some potential weaknesses revealed during the user tests, which included screen resolution and the field of view. There was one main critical deficiency found during the user tests. This was the lack of interaction with the aircraft as users were only able to interact with the flight stick and throttle lever. While this enabled the users to control many aspects of the aircraft (by using buttons and other controls fitted on the flight stick/throttle) in a training scenario a user also has to be able to interact with other switches and/or monitors in the cockpit. This was however a known limitation of the implementation and thus didn’t affect the tested parts of the simulator. The user tests also confirmed that the resolution was a potential problem, but that the overall usability was high. Thus the VR implementation had potential for use in a pilot training simulator, if the critical issues found during the user tests were solved.

  • 276.
    Gustafsson, Marcus
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Holm, Oscar
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Fuzz testing for design assurance levels2017Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    With safety critical software, it is important that the application is safe and stable. While this software can be quality tested with manual testing, automated testing has the potential to catch errors that manual testing will not. In addition there is also the possibility to save time and cost by automating the testing process. This matters when it comes to avionics components, as much time and cost is spent testing and ensuring the software does not crash or behave faulty. This research paper will focus on exploring the usefulness of automated testing when combining it with fuzz testing. It will also focus on how to fuzzy test applications classified into DAL-classifications.

  • 277.
    Gustavsson, Johan
    Linköping University, Department of Computer and Information Science, Software and Systems. Zenterio.
    A Comparative Study of Automated Test Explorers2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With modern computer systems becoming more and more complicated, theimportance of rigorous testing to ensure the quality of the product increases.This, however, means that the cost to perform tests also increases. In orderto address this problem, a lot of research has been conducted during thelast years to find a more automated way of testing software systems. Inthis thesis, different algorithms to automatically explore and test a systemhave been implemented and evaluated. In addition to this, a second setof algorithms have been implemented with the objective to isolate whichinteractions with the system were responsible for a failure. These algorithmswere also evaluated and compared against each other. In the first evaluationtwo explorers, which I called DeBruijn and LStarExplorer, were consideredsuperior to the other. The first used a DeBruijn sequence to brute forcea solution while the second used the L*-algorithm to build an FSM overthe system under test. This FSM could then be used to provide a moreaccurate description for when the failure occurred. The result from thesecond evaluation were two reducers which both tried to recreate a failureby first applying interactions performed just before the failure occurred. Ifthis was not successful, they tried interactions further and further away, untilthe failure was triggered. In addition to this, the thesis contains descriptionsabout the framework used to run the different strategies.

  • 278.
    Ha, Soonhoi
    et al.
    Seoul Natl Univ, South Korea.
    Eles, Petru Ion
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    2018 Embedded Systems Week (ESWEEK) in Torino2019In: IEEE design & test, ISSN 2168-2356, E-ISSN 2168-2364, Vol. 36, no 1, p. 68-69Article in journal (Other academic)
    Abstract [en]

    n/a

  • 279.
    Ha, Soonhoi
    et al.
    Seoul Natl Univ, South Korea.
    Eles, Petru Ion
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Editorial2018In: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, ISSN 0278-0070, E-ISSN 1937-4151, Vol. 37, no 11, p. 2187-2187Article in journal (Other academic)
    Abstract [en]

    n/a

  • 280.
    Ha, Soonhoi
    et al.
    Seoul National University, South Korea.
    Teich, Jürgen
    Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany.
    Haubelt, Christian
    Universität Rostock, Germany.
    Glaß, Michael
    Ulm University, Germany.
    Mitra, Tulika
    National University of Singapore, Singapore.
    Dömer, Rainer
    University of California, Irvine, USA.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Shrivastava, Aviral
    Arizona State University, USA.
    Gerstlauer, Andreas
    The University of Texas at Austin, USA.
    Bhattacharyya, Shuvra S.
    University of Maryland, USA; Tampere University of Technology, Finland.
    Introduction to Hardware/Software Codesign2017In: Handbook of Hardware/Software Codesign / [ed] Soonhoi Ha, Jürgen Teich, Springer Netherlands, 2017Chapter in book (Refereed)
    Abstract [en]

    Hardware/Software Codesign (HSCD) is an integral part of modern Electronic System Level (ESL) design flows. This chapter will review important aspects of hardware/software codesign flows, summarize the historical evolution of codesign techniques, and subsequently summarize each of its major branches of research and achievements that later will be presented in detail by different parts of this Handbook of Hardware/Software Codesign.

  • 281.
    Hallengren, Fredrik
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Visuell presentation av övervakningsdata2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Systemövervakning har blivit en stor del av företags IT-strukturer eftersom företag förlitar sig mer och mer på en välfungerande och högt presterande IT- struktur. När det sker problem i företags IT-strukturer så krävs det att de löses under relativt kort tid. För att hitta problemet så krävs det en mängd olika system som skall underlätta arbetet för människor som arbetar med systemövervakning och underhåll av IT-strukturer.

    För att tolka och bearbeta all den information som en IT-struktur tillhandahåller så krävs det system vars uppgift är att hjälpa människor att tolka den enorma mängd data en IT-struktur genererar. Denna rapport ger en beskrivning över hur arbetet för en systemadministratör kan förenklas med hjälp av ett integrerat övervakningssystem. Stora delar av rapporten kommer fokusera på vilken metod och protokoll som kan användas för att hämta information från olika övervakningssystem och även förslag på hur informationen kan presenteras för användaren. 

  • 282.
    Hammar, Mattias
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Parallelization of Aggregated FMUs using Static Scheduling2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis implements and evaluates static scheduling for aggregated FMUs. An aggregate FMU is several coupled FMUs placed in a single FMU. The implementation creates task graphs from the internal dependencies and connections between the coupled FMUs. These task graphs are then scheduled using two different list scheduling heuristics, MCP and HLFET. The resulting schedules are then executed in parallel by using OpenMP in the runtime. The implementation is evaluated by looking at the utilization of the schedule, the execution time of the scheduling and the speedup of the simulation. These measurements are taken on three different test models. With model exchange FMUs only a really small speedup is observed. With co-simulation models the speedup varies a lot depending on the model, the highest achieved speedup was 2.8 running on four cores.

  • 283.
    Hansson, Erik
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Code Generation and Global Optimization Techniques for a Reconfigurable PRAM-NUMA Multicore Architecture2014Licentiate thesis, monograph (Other academic)
    Abstract [en]

    In this thesis we describe techniques for code generation and global optimization for a PRAM-NUMA multicore architecture. We specifically focus on the REPLICA architecture which is a family massively multithreaded very long instruction word (VLIW) chip multiprocessors with chained functional units that has a reconfigurable emulated shared on-chip memory. The on-ship memory system supports two execution modes, PRAM and NUMA, which can be switched between at run-time.PRAM mode is considered the standard execution mode and targets mainly applications with very high thread level parallelism (TLP). In contrast, NUMA mode is optimized for sequential legacy applications and applications with low amount of TLP. Different versions of the REPLICA architecture have different number of cores, hardware threads and functional units. In order to utilize the REPLICA architecture efficiently we have made several contributionsto the development of a compiler for REPLICA target code generation. It supports both code generation for PRAM mode and NUMA mode and can generate code for different versions of the processor pipeline (i.e. for different numbers of functional units). It includes optimization phases to increase the utilization of the available functional units. We have also contributed to quantitative the evaluation of PRAM and NUMA mode. The results show that PRAM mode often suits programs with irregular memory access patterns and control flow best while NUMA mode suites regular programs better. However, for a particular program it is not always obvious which mode, PRAM or NUMA, will show best performance. To tackle this we contributed a case study for generic stencil computations, using machine learning derived cost models in order to automatically select at runtime which mode to execute in. We extended this to also include a sequence of kernels.

  • 284.
    Hansson, Erik
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Alnervik, Erik
    Kessler, Christoph
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Forsell, Martti
    VTT Technical Research Centre of Finland.
    A Quantitative Comparison of PRAM based Emulated Shared Memory Architectures to Current Multicore CPUs and GPUs2014In: 27th International Conference on Architecture of Computing Systems (ARCS), 2014, ARCS Workshops: Proc. PASA-2014 11th Workshop on Parallel Systems and Algorithms, Lübeck, Germany, Lübeck, Germany: VDE Verlag GmbH, 2014, p. 27-33Conference paper (Refereed)
    Abstract [en]

    The performance of current multicore CPUs and GPUs is limited in computations making frequent use of communication/synchronization between the subtasks executed in parallel. This is because the directory-based cache systems scale weakly and/or the cost of synchronization is high. The Emulated Shared Memory (ESM) architectures relying on multithreading and efficient synchronization mechanisms have been developed to solve these problems affecting both performance and programmability of current machines. In this paper, we compare preliminarily the performance of three hardware implemented ESM architectures with state-of-the-art multicore CPUs and GPUs. The benchmarks are selected to cover different patterns of parallel computation and therefore reveal the performance potential of ESM architectures with respect to current multicores.

  • 285.
    Hansson, Erik
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Kessler, Christoph
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Optimized selection of runtime mode for the reconfigurable PRAM-NUMA architecture REPLICA using machine-learning2014In: Euro-Par 2014: Parallel Processing Workshops: Euro-Par 2014 International Workshops, Porto, Portugal, August 25-26, 2014, Revised Selected Papers, Part II / [ed] Luis Lopes et al., Springer-Verlag New York, 2014, p. 133-145Conference paper (Refereed)
    Abstract [en]

    The massively hardware multithreaded VLIW emulated shared memory (ESM) architecture REPLICA has a dynamically reconfigurable on-chip network that offers two execution modes: PRAM and NUMA. PRAM mode is mainly suitable for applications with high amount of thread level parallelism (TLP) while NUMA mode is mainly for accelerating execution of sequential programs or programs with low TLP. Also, some types of regular data parallel algorithms execute faster in NUMA mode. It is not obvious in which mode a given program region shows the best performance. In this study we focus on generic stencil-like computations exhibiting regular control flow and memory access pattern. We use two state-of-the art machine-learning methods, C5.0 (decision trees) and Eureqa Pro (symbolic regression) to select which mode to use.We use these methods to derive different predictors based on the same training data and compare their results. The accuracy of the best derived predictors are 95% and are generated by both C5.0 and Eureqa Pro, although the latter can in some cases be more sensitive to the training data. The average speedup gained due to mode switching ranges between 1.92 to 2.23 for all generated predictors on the evaluation test cases, and using a majority voting algorithm, based on the three best predictors, we can eliminate all misclassifications.

  • 286.
    Hansson, Erik
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Kessler, Christoph
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Optimized variant-selection code generation for loops on heterogeneous multicore systems2016In: Parallel Computing: On the Road to Exascale / [ed] Gerhard R. Joubert; Hugh Leather; Mark Parsons; Frans Peters; Mark Sawyer, IOS Press, 2016, p. 103-112Conference paper (Refereed)
    Abstract [en]

    We consider the general problem of generating code for the automated selection of the expected best implementation variants for multiple subcomputations on a heterogeneous multicore system, where the program's control flow between the subcomputations is structured by sequencing and loops. A naive greedy approach as applied in previous works on multi-variant selection code generation would determine the locally best variant for each subcomputation instance but might miss globally better solutions. We present a formalization and a fast algorithm for the global variant selection problem for loop-based programs. We also show that loop unrolling can additionally improve performance, and prove an upper bound of the unroll factor which allows to keep the run-time space overhead for the variant-dispatch data structure low. We evaluate our method in case studies using an ARM big.LITTLE based system and a GPU based system where we consider optimization for both energy and performance.

  • 287.
    Hedkvist, Pierre
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Collaborative Editing of Graphical Network using Eventual Consistency2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis compares different approaches of creating a collaborative editing application using different methods such as OT, CRDT and Locking. After a comparison between these methods an implementation based on CRDT was done. The implementation of a collaborative graphical network was made such that consistency is guaranteed. The implementation uses the 2P2P-Graph which was extended in order to support moving of nodes, and uses the client-server communication model. An evaluation of the implementation was made by creating a time-complexity and a space complexity analysis. The result of the thesis includes a comparison between different methods and by an evaluation of the Extended 2P2P-Graph.

  • 288.
    Heintz, Fredrik
    et al.
    Linköping University, Department of Computer and Information Science, Artificial Intelligence and Integrated Computer Systems. Linköping University, Faculty of Science & Engineering.
    Berglund, Aseel
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Hedin, Björn
    KTH, Stockholm, Sweden.
    Kann, Viggo
    KTH, Stockholm, Sweden.
    En jämförelse mellan programsamanhållande kurser vid KTH och LiU2015In: Proceedings of 5:e Utvecklingskonferensen för Sveriges ingenjörsutbildningar (UtvSvIng), 2015Conference paper (Other academic)
    Abstract [sv]

    Programsammanhållande kurser där studenter från årskurs 1-3 gemensamt reflekterar över teman med koppling till deras studier och framtida yrkesliv finns på både KTH och Linköpings universitet (LiU). Syftet med kurserna är främst att skapa en helhet i utbildningen och ge förståelse för vad den leder till, genom att få studenterna att reflektera över sina studier och sin kommande yrkesroll. Detta leder förhoppningsvis till ökad genomströmning och minskade avhopp. Kurserna har gemensamt ursprung men har utvecklats i olika riktningar. Artikeln jämför tre programsammanhållande kurser för Datateknik KTH, Medieteknik KTH samt Data- och mjukvaruteknik Linköpings universitet.

  • 289.
    Heintz, Fredrik
    et al.
    Linköping University, Department of Computer and Information Science, Artificial Intelligence and Intergrated Computer systems. Linköping University, The Institute of Technology.
    Färnqvist, Tommy
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Återkoppling genom automaträttning2013In: Proceedings of 4:de Utvecklingskonferensen för Sveriges ingenjörsutbildningar (UtvSvIng), 2013Conference paper (Refereed)
    Abstract [sv]

    Vi har undersökt olika former av återkoppling genom automaträttning i en kurs i datastrukturer och algoritmer. 2011 undersökte vi effekterna av tävlingsliknande moment som också använder automaträttning. 2012 införde vi automaträttning av laborationerna. Vi undersökte då hur återkoppling genom automaträttning påverkar studenternasarbetssätt, prestationsgrad och relation till den examinerande personalen. Genom automaträttning får studenterna omedelbar återkoppling om deras program är tillräckligt snabbt och ger rätt svar på testdata. När programmet är korrekt och resurseffektivt kontrollerar kursassistenterna att programmet även uppfyller andra krav som att vara välskrivet och välstrukturerat. Efter kursen undersökte vi studenternas inställning till och upplevelse av automaträttning genom en enkät. Resultaten är att studenterna är positiva till automaträttning (80% av alla som svarade) och att den påverkade studenternas sätt att arbeta huvudsakligen positivt. Till exempel svarade 50% att de ansträngde sig hårdare tack vare automaträttningen. Dessutom blir rättningen mer objektiv då den görs på exakt samma sätt för alla. Vår slutsats är att återkoppling genom automaträttning ger positiva effekter och upplevs som positiv av studenterna.

  • 290.
    Heintz, Fredrik
    et al.
    Linköping University, Department of Computer and Information Science, KPLAB - Knowledge Processing Lab. Linköping University, Department of Computer and Information Science, Artificial Intelligence and Integrated Computer Systems. Linköping University, Faculty of Science & Engineering.
    Färnqvist, Tommy
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Thorén, Jesper
    Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Programutvecklingsstrategier för att öka kopplingen mellan programmering och matematik2015In: Proceedings of 5:e Utvecklingskonferensen för Sveriges ingenjörsutbildningar (UtvSvIng), 2015Conference paper (Refereed)
    Abstract [sv]

    Matematik och programmering är två viktiga inslag i civilingenjörsprogram inom data- och mjukvaruteknik. De studenter som klarar dessa kurser klarar sannolikt resten av utbildningen. Idag har fler studenter programmering än matematik som huvudsakligt intresse. Därför har Linköpings universitet aktivt jobbat med olika strategier för att öka kopplingen mellan programmering och matematik, främst i de inledande kurserna. För att undersöka studenternas attityder till matematik och programmering har vi genomfört flera enkätstudier som bl.a. visar att intresset för matematik är stort men intresset för programmering ännu större och att studenterna tror de kommer ha betydligt mer nytta av programmering än matematik under sin karriär. Texten är tänkt som grund för en diskussion kring hur kopplingarna mellan matematik och programmering kan göras tydligare och starkare.

  • 291.
    Heintz, Fredrik
    et al.
    Linköping University, Department of Computer and Information Science, Artificial Intelligence and Integrated Computer Systems. Linköping University, Faculty of Science & Engineering.
    Mannila, Linda
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Färnqvist, Tommy
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    A Review of Models for Introducing Computational Thinking, Computer Science and Computing in K-12 Education.2016In: Proceedings of the 46th Frontiers in Education (FIE), IEEE , 2016Conference paper (Refereed)
    Abstract [en]

    Computing is becoming ever increasingly importantto our society. However, computing in primary and secondaryeducation has not been well developed. Computing has traditionallybeen primarily a university level discipline and there areno widely accepted general standards for what computing at K–12 level entails. Also, as the interest in this area is rather new,the amount of research conducted in the field is still limited. Inthis paper we review how 10 different countries have approachedintroducing computing into their K–12 education. The countriesare Australia, England, Estonia, Finland, New Zealand, Norway,Sweden, South Korea, Poland and USA.

    The studied countries either emphasize digital competenciestogether with programming or the broader subject of computingor computer science. Computational thinking is rarely mentionedexplicitly, but the ideas are often included in some form. Themost common model is to make it compulsory in primary schooland elective in secondary school. A few countries have made itcompulsory in both. While some countries have only introducedit in secondary school.

  • 292.
    Hellsing, Mattias
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Albin, Odervall
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Efficient Multi-Core Implementation of the IPsec Encapsulating Security Payload Protocol for a Single Security Association2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As the mobile Internet traffic increases, the workload of the base stations processing this traffic increases with it. To cope with this, the telecommunication providers responsible for the systems deployed in these base stations have looked to parallelism. This, together with the fact that these providers have a vested interest in protecting their users' data from potential attackers, means that there is a need for efficient parallel packet processing software which handles encryption as well as authentication. A well known protocol for encryption and authentication of IP packets is the Encapsulating Security Payload (ESP) protocol of the IPsec protocol suite. IPsec establishes simplex connections, called Security Associations (SA), between entities that wish to communicate. This thesis investigates a special case of this problem where the work of encrypting and authenticating the packets within a single SA is parallelized. This problem was investigated by developing and comparing two multi-threaded implementations based on the Eventdev, an event driven programming library, and ring buffer libraries of Data Plane Development Kit (DPDK). One additional Eventdev-based implementation was also investigated which schedules linked lists of packets, instead of single packets, in an attempt to reduce the overhead of scheduling packets to the worker cores. These implementations were then evaluated in terms of throughput, latency, speedup, and last level cache miss rates. The results showed that the ring buffer-based implementation performed the best in all metrics while the single packet-scheduling Eventdev-based implementation was outperformed by the one using linked lists of packets. It was shown that the packet generation, which was done by the receiving core, was the main limiting factor for all implementations. In addition, the memory resources such as the memory bus, memory controller and prefetching hardware were shown to likely be an area of contention and a possible bottleneck as the packet generation rate increases. The conclusion drawn from this was that a parallelized packet retrieval solution such as Receive Side Scaling (RSS) together with minimizing memory resource contention is necessary to further improve performance.

  • 293.
    Hellström, Jesper
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Moberg, Anton
    Linköping University, Department of Computer and Information Science, Software and Systems.
    A Lightweight Secure Development Process for Developers2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Following a secure development process when developing software can greatly increase the security of the software. Several secure development processes have been developed and are available for companies and organizations to adopt. However, the processes can be expensive and complex to adopt in terms of expertise, education, time, and other resources.In this thesis, a software service, developed by a small IT-consulting company, was tested with security tools and manual code review to find security vulnerabilities. These vulnerabilities showed that there was room for security improvement in the software development life cycle. Therefore, a lightweight secure development process that can be used by developers, is proposed. The secure development process called Lightweight Developer-Oriented Security Process (LDOSP) is based on activities from other secure development processes and the choice of these activities were based on interviews with representatives of the IT-consulting company. The interviews showed that the process would need to be lightweight, time- and cost-efficient, and possible to be performed by a developer without extensive security experience. LDOSP contains 11 activities spread across different phases of the software development life cycle and an exemplification of the process was made to simplify the adoption of LDOSP.

  • 294.
    Helén, Ludvig
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Automating Text Categorization with Machine Learning: Error Responsibility in a multi-layer hierarchy2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The company Ericsson is taking steps towards embracing automating techniques and applying them to their product development cycle. Ericsson wants to apply machine learning techniques to automate the evaluation of a text categorization problem of error reports, or trouble reports (TRs). An excess of 100,000 TRs are handled annually.

    This thesis presents two possible solutions for solving the routing problems where one technique uses traditional classifiers (Multinomial Naive Bayes and Support Vector Machines) for deciding the route through the company hierarchy where a specific TR belongs. The other solution utilizes a Convolutional Neural Network for translating the TRs into low-dimensional word vectors, or word embeddings, in order to be able to classify what group within the company should be responsible for the handling of the TR. The traditional classifiers achieve up to 83% accuracy and the Convolutional Neural Network achieve up to 71% accuracy in the task of predicting the correct class for a specific TR.

  • 295.
    Henrik, Thoreson
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Robin, Wesslund
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Naive Bayes-klassificering av förarbeteende2017Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    To be able to classify a driving style implies that you classify a driving behaviour, which is the foundation of safety and environmental driving classification.

    In this thesis we have let two drivers drive a car in an attempt to classify, with a desired accuracy of around 90%, which one of us drove the car. This was done by exclusively using speed and rpm data values provided from the OBD:II port of the car via the CAN-bus. We approched this problem like you would a text classification one, thus using two common models of Naive Bayes — Multinominal and Gaussian Naive Bayes together with N-gram and discretization.

    We found that using Multinominal Naive Bayes consisting of 4-gram resulted in an avarage accuracy of 91.48% in predicting the driver, non-discretized speed and discretized rpm values.

  • 296.
    Henriksson, Jonas
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Implementation of a real-time Fast Fourier Transform on a Graphics Processing Unit with data streamed from a high-performance digitizer2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis we evaluate the prospects of performing real-time digital signal processing on a graphics processing unit (GPU) when linked together with a high-performance digitizer. A graphics card is acquired and an implementation developed that address issues such as transportation of data and capability of coping with the throughput of the data stream. Furthermore, it consists of an algorithm for executing consecutive fast Fourier transforms on the digitized signal together with averaging and visualization of the output spectrum.

    An empirical approach has been used when researching different available options for streaming data. For better performance, an analysis of the introduced noise of using single-precision over double-precision has been performed to decide on the required precision in the context of this thesis. The choice of graphics card is based on an empirical investigation coupled with a measurement-based approach.

    An implementation in single-precision with streaming from the digitizer, by means of double buffering in CPU RAM, capable of speeds up to 3.0 GB/s is presented. Measurements indicate that even higher bandwidths are possible without overflowing the GPU. Tests show that the implementation is capable of computing the spectrum for transform sizes of , however measurements indicate that higher and lower transform sizes are possible. The results of the computations are visualized in real-time.

  • 297.
    Henrio, Ludovic
    et al.
    Univ Cote Azur, France.
    Kessler, Christoph
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Li, Lu
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Ensuring Memory Consistency in Heterogeneous Systems Based on Access Mode Declarations2018In: PROCEEDINGS 2018 INTERNATIONAL CONFERENCE ON HIGH PERFORMANCE COMPUTING and SIMULATION (HPCS), IEEE , 2018, p. 716-723Conference paper (Refereed)
    Abstract [en]

    Running a program on disjoint memory spaces requires to address memory consistency issues and to perform transfers so that the program always accesses the right data. Several approaches exist to ensure the consistency of the memory accessed, we are interested here in the verification of a declarative approach where each component of a computation is annotated with an access mode declaring which part of the memory is read or written by the component. The programming framework uses the component annotations to guarantee the validity of the memory accesses. This is the mechanism used in VectorPU, a C++ library for programming CPU-GPU heterogeneous systems and this article proves the correctness of the software cache-coherence mechanism used in the library. Beyond the scope of VectorPU, this article can be considered as a simple and effective formalisation of memory consistency mechanisms based on the explicit declaration of the effect of each component on each memory space.

  • 298.
    Hero-Ek, Pontus
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Improving AR visualizationwith Kalman filtering andhorizon-based orientation: – To prevent boats to run aground at sea2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis researched the possibility of improving the compass of smartphones as theearth’s magnetic field is not strong and is easily disturbed, either by the environment ortechnology. The compass is used in Augmented Reality (AR) when the AR visualizationshould correspond to a position on earth. The issue lies in oscillating input values to thecompass that reduces the AR experience.To improve the AR experience without the use of external equipment, this work tried toboth filter the incoming values with a Kalman filter and to know the direction by capturingan image with a horizon that was image processed. The Kalman filter achieved a reductionin incoming disturbances and the horizon was matched against a panorama image thatwas generated from 3D data. The thesis starts off with requirements and contents of ARand goes through the different approaches that begins with a LAS point cloud and ends inmatching horizons with normalized cross-correlation.This thesis furthermore measures performance and battery drainage of the built applicationon three different smartphones that are nearly a year apart each. Drift was alsomeasured as it is a common issue if there is no earthly orientation to correct itself unto,for instance the magnetometer. This showed that these methods can be used on OnePlus2, Samsung Galaxy S7, and Samsung Galaxy S8, there is a steady performance and efficiencyincrease in each generation and that ARCore causes less drift. Furthermore thisthesis shows the difference between a compass and a local orientation with an offset.The application that was made focused to work at sea but it was also tested on buildingswith good results. The application also underwent usability tests that showed that theapplied functionalities improved the AR-experience. The conclusion shows that it is possibleto improve the orientation of smartphones. Albeit it can go wrong sometimes which iswhy this thesis also presents two ways to indicate that the heading is off.

  • 299.
    Holm, Rasmus
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Energy-Efficient Mobile Communication with Cached Signal Maps2016Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Data communication over cellular networks is expensive for the mobile device in terms of energy, especially when the received signal strength (RSS) is low. The mobile device needs to amplify its transmission power to compensate for noise leading to an increased energy consumption. This thesis focuses on developing a RSS map for the third generation cellular technology (3G) which can be stored locally at the mobile device, and can be used for avoiding expensive communication in low RSS areas.

    The proposed signal map is created by crowdsourced information collected from several mobile devices. An application is used to collect data in the mobile device of the user and the application periodically sends the information back to the server which computes the total signal map.

    The signal map is composed of three levels of information: RSS information, data rate tests and estimated energy levels. The energy level categorizes the energy consumption of an area into "High", "Medium" or "Low" based on the RSS, data rate test information and an energy model developed from physical power measurements. The coarse categorization provides an estimation of the energy consumption at each location. It is evaluated by collecting data traces on a smartphone at different locations and comparing the measured energy consumption at each location to the energy level categories of the map.

    The RSS prediction is preliminarily evaluated by collecting new data along a path and comparing how well it correlates to the signal map. The evaluation in this thesis shows that with the current collected data there are not enough observations in the map to properly estimate the RSS. However, we believe that with more observations a more accurate evaluation could be done.

  • 300.
    Horga, Adrian
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Chattopadhyay, Sudipta
    Singapore University of Technology and Design (SUTD), Information Systems Technology and Design (ISTD), Singapore.
    Eles, Petru Ion
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Measurement Based Execution Time Analysis of GPGPU Programs via SE+GA2018Conference paper (Refereed)
    Abstract [en]

    Understanding the execution time is critical for embedded, real-time applications. Worst-case execution time (WCET) is an important metric to check the real-time constraints imposed on embedded applications. For complex execution platforms, such as graphics processing units (GPUs), analysis of WCET imposes great challenges due to the complex characteristics of GPU architecture as well as GPU program semantics. In this paper, we propose GDivAn, a measurement-based WCET analysis tool for arbitrary GPU kernels. GDivAn systematically combines the strength of symbolic execution (SE) and genetic algorithm (GA) to maintain both the scalability and the effectiveness of the analysis process. Our evaluation with several open-source GPU kernels reveals the efficiency of GDivAn.

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